Magnetic multipositioning actuators



'May 11, 1965 JJFLORA 3,183,410

MAGNETIC MULTIPOSI'I'IONING ACTUATORS Filed Dec. 30, 1960 INV EN TOR. JAMES FLORA United States Patent 3,183,410 MAGNETIC MULTH'OQI'HGNENG ACTUATGRS James Flora, Santa Clara, Calif assignor to international Business Machines Corporation, New York, N.Y., a corporation of New York Filed Dec. 30, 1960, Ser. No. 7%786 6 Claims. (@l. 3l7125) The invention relates to magnetic actuators, and it particularly pertains to magnetic multipositioning actuators for linearly positioning utilization devices in series of discrete positions.

There are known arrangements for positioning apparatus with magnetic actuators. Despite a number of highly satisfactory dual position actuators which position accurately against mechanical stops (as distinguishing from mechanical detents), there has been little or no success in extending the principles of the dual position actuator to magnetic multipositioning actuators. As used in the specification, the prefix multiis to be construed in the stricter connotation of three or more positions. While magnetic devices are known for multipositioning an armature or" relatively high permeability material in a varying magnetic field, insofar as the applicant is aware, only a coarse positioning is achieved and that is accompanied by oscillations of the armature which are tolerable only for a few practical applications. Hence, the only practical systems of the prior art rely on the magnetic system for movement into the vicinity of the desired position and thereafter rely on mechanical detenting structure forprecisely setting the apparatus into and holding it in the desired position until it is desired to move the apparatus into another discrete position.

An object of the invention is to provide a magnetic multipositioning actuator capable of more precise positioning than heretofore available with known structures.

Another object of the invention is to provide a magnetic multipositioning actuator exhibiting little or no oscillation at the selected positions.

A further object of the invention is to provide a magnetic multipositioning actuator of accurate setting and repeatability, free from oscillation or hunting, and without resorting to mechanical detenting.

According to the invention a linear multipositioning magnetic actuator is obtained by influencing an armature of material of high magnetic retentivity, preferably a permanent magnet of relatively high magnetic strength, by two opposing magnetic fields. The magnetic flux of one, the tractive, field extends in the same direction as the magnetic fiux of the armature and the magnetic flux of the other, the opposing field is in opposition to that of the armature to precisely position it with respect to the magnetic null. In such a magnetic system according to the invention, the vector sum of the magnetic forces of the tractive magnetic field and the magnetic field of the armature is equal and opposite to the force of the opposing magnetic field, whereby oscillation or huntin is reduced to a minimum and the system is always operating on a minor hysteresis loop.

In one embodiment of the invention, the opposing magnetic fields are generated by means of a centrally tapped inductor, or a number of series connected solenoid windings, having the terminals connected together to form a closed electric loop and means to apply direct potential between the interconnected terminals of the inductor, or solenoid windings, and one of the taps or interconnections between the solenoid windings; and a permanent magnet armature is positioned in the centrally tapped inductor, or series connected solenoid windings, in accordance with the relative strengths of the magnetic fields.

In another embodiment of the invention, the opposing magnetic fields are established in a core member of mateice connecting the ends of the hollow and parallel portions to form a closed magnetic path. Windings are arranged about the other portions of the magnetic core member and connected to a source of direct potential for exciting the core member with opposing fields of flux.

In all of the embodiments of the invention, the magnetic field producing windings are polarized to provide opposing fields of magnetic flux and the direct potential is applied through circuitry arranged to difierentially energize the windings in accordance with the desired disposition of the armature to be positioned. it will be recognized that the embodiments of the invention each have one state of operation in which the opposing magnetic fields resulting from the application of the direct potential are equal and the term difierentially energized as employed in this specification, is to be construed to include this one state as well as those states wherein the two magnetic fields differ appreciably.

Further, according to the invention, the length of the armature is not restricted as in the prior art arrangements but may be at least of the order of the span of the intermediate taps of the tapped inductor or the length of the parallel portion of the core member; both of which are of the order of the length of the stroke of the armature; and the length of the armature is preferably of the order of the length of the tapped inductor or the length of the here.

Further according to the invention, improved results are obtained with an armature in the form of a magnet of consequent poles. This may consist of two permanent magnets arranged on'the shaft coupling the utilization device with like poles together at the center of the armature, or alternatively, a bar of high retentivity magnetic material may be so magnetized in construction.

In order that the practical aspects of the invention may be readily realized in practice, several embodiments of the invention are described hereinafter with reference to the accompanying drawing forming a part of the specification and in which:

FIG. 1 depicts the mechanical structure of a magnetic multipositioning actuator according to the invention;

FIG. 2 is a schematic diagram of an electric circuit embodying the invention and incorporating the structure illustrated in FIG. 1;

PEG. 3 is a circuit diagram of a different embodiment of the invention;

FIG. 4 depicts the mechanical structure of still another embodiment of the invention; and

FIGS. 5 and 6 are schematic diagrams of electric circuits embodying the invention and incorporating the structure depicted in FIG. 4.

FIGS. 1 and 2 depict a basic embodiment of the invention comprising a non-magnetic tubular sleeve member 12 in which an armature 14 of material of high magnetic retentivity, preferably a permanent magnet, is arranged for longitudinal movement carrying non-magnetic shafts 16 and 17, one or both of which may be coupled to utilization devices to be positioned. The armature 14 may, for example, be made of a material known to the artisan as Alnico V, consisting of eight parts of aluminum, fourteen parts nickel, twenty-four parts of cobalt, three parts of copper, and fifty-one parts of iron. Preferably, the sleeve 12 and the armature 14 are cylindrical in order not to restrain rotational movement, although it is contemplated that, in some instances, such configu'rations may be used to restrain or force rotational movement as a practical application may require. A bobbin 18 of non-magnetic material surrounds the sleeve member 12 to support a centrally tapped inductor, shown in FIG. 1 as a series of separate solenoid windings 20, 2f, 28, and 29. Gne end of the first winding 23 is connected to a conductive tab 30 forming a terminal and the other end is connected to a conductive tab 31 forming a central tap to which an end of the second winding 21 is also connected to place the coils in magnetic flux aiding relationship. Similarly, remaining winding ends are connected to conductive tabs 32, 33, 3%, and 39 forming the central taps and to the remaining conductive tab 49 forming a terminal of the inductor.

The centrally tapped inductor is energized differentially as shown in the schematic diagram of FIG. 2 wherein the intermediate tabs 3139 are connected respectively to contacts 31 and 39 of an electric selector switch 41 having a switch blade or arm 42 connected to one terminal of a source of direct potential, shown as a battery 44, the other terminal of which is connected to the inductor terminal tabs 30 and 4t). Energized as shown the tapped inductor will exhibit like poles at the ends of the windings 22 and 23' connected to the switch contacts 33 and opposite poles will be set up at the remote terminals of the inductor connector to the terminal tabs 30 and 4t According to the invention of the armature advantageously may be long with respect to the width of the individual solenoid windings. Preferably it is of a length at least as long as the span of the taps definedby the tabs connected to switch contacts 31' and 39 and may be of length equal to the length of the entire inductor. The maximum length depends to some extent upon the maxi mum stroke of the inductor; the important criterion being the maximum portion of the armature which extends outside the inductor at the ends of the stroke. The return flux path between the armature 14' and the tapped inductor must be short enough to prevent substantial demagnetization of that portion of the armature which 6X- tends outside the field of the tapped inductor. According to the invention, the armature 14' is positioned within the tapped inductor with the north pole aligned with the north pole of the solenoid Winding establishing the tractive magnetic flux so that the magnetic flux of the tractive winding and the magnetic flux of the permanent magnet armature 14' extend in the same direction and in opposition to the magnetic flux generated by the opposing winding. For each given position of the switch arm 42, the armature 14 will be moved toa position in accordance with equilibrium of the force developed by the tractive winding and the armature and the force developed by the opposing winding. In the embodiment schematically illustrated by FIG. 2, the innermost end of the armature M will not be directly above the tab selected by the switch Contact 33' but will be somewhere to the right as the armature l4 will tend to be m-ovedmore centrally of the tractive winding between the switch contact 33 and the terminal tab l0.

With the tabs of the windings connected to the switch contacts Err-39 connecting winding sections of uniform width and magnetic force developing characteristics, the armature 14 will be moved through distances which differ slightly from the winding section widths as the switch arm 4-2 is moved to different switch contacts; however, if uniform positioning is desired, the widths of the individual solenoid windings may be varied according to known formulae in order to produce uniform positioning increments.

A variation of the basic arrangement is illustrated in FIG. 3, in which'embodiment the bipolar magnet armature lid is replaced by a consequent pole armature 14". The consequent pole armature 14" may be constructed by arranging two permanent magnets on the shaft coupling the armature to the utilization device with proper like poles together at the center of the arrangement, or a single rod of high retentivity magnetic material may be so magnetized in manufacture. In operation, the consequent poles of the armature l4 follow the same basic magnetic laws as set forth for the previous embodiments. Improved operation is obtained in that center of the armature 1d sore nearly coincides with the selected tab between the solenoid winding sections because the tractive winding for one half of the armature 14" acts at the same time as the opposing winding for the other half of the armature l4" tending to provide a better balance of forces in operation. In the arrangement shown in FIG. 3, when the switch arm 42 is on the switch contact 35 connected to the center tap of the inductor, the center of the armature 14 with consequent poles will be directly above the center tap of the winding. 'However, as the armature 14" moves away from the center tap to either side, the increrrrent of movement will be less than the width of a winding section and will decrease as the armature moves farther from the center tap; the reason being the tendency for each winding section to center the portion of the armature 14 therein. Uniform increments of movement can be obtained by varying the Width of the winding sections accordingly.

FIG. 4 depicts the structural arrangement of an improved embodiment of the invention wherein a magnetic core member 50 of material of high magnetic permeability is employed to concentrate the magnetic flux at the desired location with respect to the permanent magnet armature 14. The core member 5% comprises a portion 52 hollowed by a bore in which the sleeve member of non-magnetic material 12 is inserted and in which sleeve member the armature 14 is arranged for longitudinal movement. Parallel to the hollow core portion 52 is an elongated complementary core portion 54 having the ends magnetically connected to the hollow core portion 52 by means of other core portions 56 and 58 about which respective exciting solenoid windings as and 68 are arranged. The complementary parallel core portion 54 lies substantially parallel to the hollow core portion 52 over the distance substantially equal to the usable stroke of the armature M. The gap 6%) between the parallel core portion 54 and the hollow core portion 52 is sufiiciently wide to prevent undue flux leakage and sufficiently narrow to provide for passage of flux as desired. Preferably the central portion of the gap 60 is a little narrower than the width of the complementary core portion 54-, and the ends of the gap are wider than the central position; the transition being in the form of a smooth exponential curve.

FIG. 5 is a schematic diagram of a circuit energizing the multipositioning actuator shown in MG. 4. A potentiometer 7d is connected so that the resistance strip 71 is in series with the exciting windings es and as and a direct potential source, shown as a battery 54, is connected between the arm 72 of the potentiometer 7t and the terminals of the exciting windings as and 63'. Alternative ly, the continuously variable potentiometer 7%? may be replaced by a switch and a plurality of fixed resistance elements in a manner suggested by the schematic diagram of FIG. 6 wherein one winding as is connected through switch 80 and contacts 81-85 connected to the junctions between the series connected resistors 91-94. In the arrangement shown in FIG. 6, the other exciting winding 68' is connected directly across the potential source'and the current to the one winding so only is varicd; however, other expedient circuits will be obvious to the artisan.

Referring to FIG. 4, two opposing fields of magnetic flux are developed in the core 5% by exciting the windings as and 6S. ()ne flux path starts, say, in the end core portion 56 beneath the winding 66, traverses a part of the core portion 56 to the core portion 52 toward the center thereof, bridges the gap till to the complementary core portion 54 and travels back to the core portion 54 to the 'end portion at beneath the winding 66. The other flux path, similarly begins under core portion 58 beneath the winding 68, travels through the portion of the core mem ber 58 to the hollow core portion 52, bridges the gap 60,.

through the complementary core portion, and travels back through the core portion 54 and part of the core portion 58 to the portion beneath the winding 68. Thus, the lines of flux of the two magnetic fields travel in opposite directions in the core member 60. There will be a high con centration of electromagnetic fiux bridging the gap 60 at the point where the opposing magnetic fields are equal in strength. The armature 14 will be attracted to and held in position within the bore of the core member 52 at a point determined by the forces resulting from the two magnetic fields developed in the core member 50 and the magnetic field of the armature 14; following the same laws as followed in the arrangement shown in FIG. 1. Improved results will be attained by the substitution for the bipolar armature 14 by an armature with consequent poles as discussed hereinbefore with respect to the embodiments illustrated in FIGS. 1-3.

The arrangement illustrated in FIGS. 4-6, like the arrangements described earlier, will provide non-uniform increments of movement for uniform increments of applied current, however, it is a relatively simple matter for those skilled in the art to adjust the electric current increments, as by changing the values of the series connected resistors 91-94, to provide uniform increments of movement for positioning the utilization device.

It should be noted that the invention is not limited to straight-line positioning of an armature and the associated utilization device at a magnetic system according to the invention may be arranged in the plane to lie on the arc of a circle to provide curvilinear motion, and with the proper mechanical structure, rotational movement about the center of curvature of the circle may be obtained.

While the invention has been particularly shown and described with reference to preferred embodiments there- Of, it will be understood by those skilled in the art that the foregoing and other changes in the form and details may be made therein without departing from the spirit and scope of the invention.

The invention claimed is:

1. A magnetic positioning device including,

a tubular sleeve member of nonmagnetic material,

a core member of material of low magnetic retentivity and high permeability forming a closed magnetic path,

a portion of said member substantially surrounding said sleeve member,

a further portion intermediate the ends of the first said portion lying close to and parallel to the first said portion surrounding said sleeve member and two other portions lying at the ends of the first said portions and completing said closed magnetic path, electromagnetic windings disposed about said other portions of said core member,

a magnetic armature disposed for longitudinal movement in said sleeve member,

means coupling said armature to a utilization device,

and

means for energizing said windings differentially to produce opposing magnetic fields in said core member and to cause said armature to be positioned within said sleeve member in accordance with the null be tween said opposing magnetic fields.

2. A magnetic positioning device including,

a tubular sleeve member of nonmagnetic material,

a core member of material of high permeability fOrming a closed magnetic path.

a portion of said core member substantially surrounding said sleeve member,

a further portion lying close to and parallel to the first said portion intermediate the ends of the first said portion surrounding said sleeve member, and

two other portions lying at the ends of said sleeve member and said further portion and completing said closed magnetic path,

two windings disposed about said other portions of said core member,

a magnetic armature having consequent poles disposed for longitudinal movement in said sleeve member,

means coupling said armature to a utilization device,

and

means for energizing said windings differentially to produce opposing magnetic fields in said core member and to cause said armature to be positioned within said sleeve member in accordance with the null between the consequent poles and said opposing magnetic fields.

3. A magnetic positioning device including a tubular sleeve member of non-magnetic material,

a winding arranged about said sleeve member,

said winding having interconnected terminals and a plurality of taps intermediate said terminals,

a unitary permanent magnet armature of length at least as great as the total length of said winding between the first and last of said intermediate taps and arranged for longitudinal movement Within said sleeve member, and

means to apply unidirectional electric potential between said interconnected terminals and one of said intermediate taps for producing two magnetic fields of opposing magnetic flux about said armature to position the same within said sleeve member in accordance with the null between said opposing magnetic fields.

4. A magnetic positioning device as defined in claim 3 and wherein said taps are spaced apart by distances at which equal increments of movement of said armature are obtained.

5. A magnetic positioning device including a tubular sleeve member of non-magnetic material,

at least two windings arranged about said sleeve member,

an elongated unitary permanent magnet armature comprising consequent poles intermediate the ends thereof and arranged for longitudinal movement within said sleeve member,

a source of unidirectional electric potential, and

electric circuitry interconnecting said windings and said source for producing two magnetic fields of opposing magnetic flux about said armature,

to position the same within said sleeve member in accordance with the null between said opposing magnetic fields.

6. A magnetic positioning device including a tubular sleeve member of non-magnetic material,

a winding arranged about said sleeve member,

said winding having interconnected terminals and a plurality of taps intermediate said terminals,

a unitary permanent magnet armature comprising consequent poles intermediate the ends thereof and arranged for longitudinal movement within said sleeve member, and

means to apply unidirectional electric potential between said interconnected terminals and one of said taps for producing two magnetic fields of opposing magnetic flux about said armature to position the same within said sleeve member in accordance with the null between said opposing magnetic fields.

References Cited by the Examiner UNITED STATES PATENTS 1,161,819 11/15 Grob 3l7-123X 2,134,777 11/38 Clancy 317-190 2,833,968 5/58 Karlson 317199 2,987,656 6/61 Handshuh et a1 317123 X 2,989,666 6/61 Brenner et al 317l X 3,022,400 2/62 Von Ahlefeldt 317l91 3,135,880 6/64 Olson et al 317-123 SAMUEL BERNSTEIN, Primary Examiner. 

3. A MAGNETIC POSITIONING DEVICE INCLUDING A TUBULAR SLEEVE MEMBER OF NON-MAGNETIC MATERIAL, A WINDING ARRANGED ABOUT SAID SLEEVE MEMBER, SAID WINDING HAVING INTERCONNECTED TERMINALS AND A PLURALITY OF TAPS INTERMEDIATE SAID TERMINALS, A UNITARY PERMANENT MAGNET ARMATURE OF LENGTH AT LEAST AS GREAT AS THE TOTAL LENGTH OF SAID WINDING BETWEEN THE FIRST AND LAST OF SAID INTERMEDIATE TAPS AND ARRANGED FOR LONGITUDINAL MOVEMENT WITHIN SAID SLEEVE MEMBER, AND MEANS TO APPLY UNIDIRECTIONAL ELECTRIC POTENTIAL BETWEEN SAID INTERCONNECTED TERMINALS AND ONE OF SAID INTERMEDIATE TAPS FOR PRODUCING TWO MAGNETIC FIELDS OF OPPOSING MAGNETIC FLUX ABOUT SAID ARMATURE TO POSITION THE SAME WITHIN SAID SLEEVE MEMBER IN ACCORDANCE WITH THE NULL BETWEEN SAID OPPOSING MAGNETIC FIELDS. 